The unlocking in 2021 primarily resulted from interest rate fluctuations and the impact of management actions in the low interest rate environment during the period. The unlocking in 2020 primarily resulted from interest rate fluctuations. The unlocking in 2019 primarily resulted from unlocking surrender rates and reinsurance as well as refinements of expense loads. These were partially offset by interest rate fluctuations. In addition, we recorded a $0.7 million reserve decrease in 2021, a $0.4 million reserve increase in 2020, and a $0.2 million reserve decrease in 2019 related to the impacts of unlocking. We diversify our commercial mortgage loan portfolio both geographically and by property type to reduce certain risks, including local and regional physical and economic exposures. However, diversification may not always sufficiently mitigate these risks. Concentration risk exposes us to potential losses from an economic downturn, certain catastrophes, and natural disasters that may affect geographic locations where we have mortgage loans. We would not expect an occurrence in any of these geographic locations to have a material adverse effect on our business, financial position, or financial statements. However, we cannot provide assurance that such risks could not have such material adverse effects.Under the laws of certain states, environmental contamination of a property may result in a lien on the property to secure recovery of the costs of cleanup. In some states, such a lien has priority over the lien of an existing mortgage against such property. As a commercial mortgage lender, we customarily conduct environmental assessments prior to making commercial mortgage loans secured by real estate and before taking title on real estate. Based on our environmental assessments, we believe that any compliance costs associated with environmental laws and regulations or any remediation of affected properties would not have a material adverse effect on our business, financial position, or financial statements. However, we cannot provide assurance that material compliance costs will not be incurred.